Gritty Tenderloin cleans up with Japanese bathhouse Onsen

1of 14Onsen is a new, Japanese-style bathhouse with a restaurant, soaking tub and massage treatments at 466 Eddy St., the site of a former auto repair shop.Photo: Raquel Venancio Photography

2of 14Onsen, a new, Japanese-style bathhouse, also has a restaurant that serves teas, kombucha, sake, wine, beer and cocktails. Benches in the restaurant and other wooden decor are made of redwood planks milled from trees that Simmons recovered from rivers and logging roads in Northern California over the past 20 years.Photo: Grace Sager

3of 14Onsen’s restaurant offers a menu by chef George Meza that changes daily, but focuses on Japanese-style fish, meats, noodles and vegetables. Teas and kombuchas along with sakes, wine, beer and cocktails are served.Photo: Grace Sager

4of 14Onsen transformed the space, which used to be a former auto repair shop.Photo: Raquel Venancio Photography

14of 14Onsen is at 466 Eddy St., the site of a former auto repair shop.Photo: Raquel Venancio Photography

Onsen is a word for the communal baths located in the volcanic hot springs of Japan’s countryside. The Tenderloin has no volcanoes, but it is erupting in new businesses changing the once-gritty landscape, from tech companies, museums and bars to a new bathhouse named — what else? — Onsen.

Owners of the Japanese-style establishment with a bubbling eight-person soaking tub, six treatment rooms and a restaurant at 466 Eddy St. hope it will become a hangout for couples’ date nights or socializing with groups of friends.

Husband-wife team Sunny Simmons, a contractor, and Caroline Smith, an artist, have spent the past few years transforming the building — once a carriage house and later an auto repair shop — into a snug, even wholesome, haven. Like most of the structures in the area, known as the Uptown Tenderloin National Register Historic District, the shop was originally built between 1906 and the 1930s.

“Our thought was we would create a space where somebody could come and spend hours,” Simmons said. “It’s a little oasis in the city where you can get out of everything.”

The front door leads to Onsen’s small restaurant. On the menu: tea and kombucha, sake, wine, beer and cocktails ($4-$13), and Asian-inspired food that changes daily based on market availability, ranging from small bites, skewers, plates and sweets ($6-$16). The menu was designed by chef George Meza, formerly of Ame and Oro.

The treatment rooms, along with the communal bath, steam room and sauna, are located at the rear. The question of bathing suits is answered by a policy that requires covering up on co-ed days (Friday, Saturday and Sunday), and allows nudity on single-sex days (women only on Mondays and Thursdays; men only on Wednesdays). If you forget to bring a swimsuit, no problem — one will be provided.

Onsen’s tub is a tranquil spot — a quiet zone — in the afternoon, but music is piped into the bathhouse at night for an upbeat feel. “We wanted it to be social, not totally Zen-ned out with no one talking to each other,” Smith explained.

Despite its artistic redwood beams, pendant lamps and hand-stitched artworks, permits for the bathhouse took some wrangling; the city wasn’t keen on allowing massage services in the Tenderloin, but in the case of Onsen, made an exception. Massage and acupuncture are expected to begin in the new year. (City ordinance still prohibits the operation of massage establishments between 10 p.m. and 7 a.m.)

Open for a little more than a month, Onsen is already a hit — the restaurant recently served 80 people in one night and the tub served 70 guests in one day. The couple aim to please more than destination-seekers with flush wallets: They’re offering free acupuncture to the area’s military veterans and discounts to local residents.

“The people who live in this neighborhood have seen me every single day for three years,” Simmons said. “I talk with them, we hang out with them, they all know us, and they appreciate that we’re willing to put that time and effort into becoming a part of their community.”

Soaking: Perhaps the most unique feature at Onsen is its soaking tub. It’s been built into a pit in which automotive fluids were once drained. It is heated to a maximum 104 degrees and can hold eight people. A cold-plunge shower, steam room and sauna round out the water treatments.

Woodworking: Benches in the restaurant, the shelves and other wooden decor are made of redwood planks milled from trees that Simmons recovered from rivers and logging roads in Northern California over the past 20 years.

Decor: A bamboo planter on one wall and hanging gardens on two others add a touch of the outdoors to the former auto plant. Black chalkboards salvaged from a school in Ohio have been coated with a sealer and line the walls of the showers, and serve as tabletops in the restaurant. Smith used fabric and dyed it indigo, and stitched it to create cloth panels for doorways. She also painted pictures for framed artwork in massage rooms and used scraps from old blue jeans for a wall hanging near the massage reception desk. Other works by local artists are also on display.

Massage: A variety of massage and acupuncture treatments will be offered at the bathhouse, in sessions to range from 45 to 90 minutes. Floors are heated, and massage tables have heated blankets.

Showers: Showers are lined with sealed black chalkboards salvaged from an Ohio school. Shampoos, conditioners and soaps by Shikai of Santa Rosa are featured.

Bathhouse rules: Adults only (no children); no alcohol allowed, and a photo I.D. is required for admittance to the tub. The bath is open from 11 a.m. to 10 p.m. every day but Saturday, when it’s open until 1 a.m.. A soak, with a two-hour time limit, is $30.

Pro tip: Reservations for tub time are accepted only with a dinner reservation, or in combination with massage or acupuncture treatments, coming soon. Walk-ins are accepted if there is room in the tub; if not, you’re put on a wait list. Call ahead to see how busy the bathhouse is.

Carolyne Zinko, a native of Wisconsin, joined The San Francisco Chronicle in 1993 as a news reporter covering Peninsula crime, city government and political races. She worked as the paper’s society columnist from 2000 to 2004, when she wrote about the lifestyles of the rich but not necessarily famous. Since then, she has worked for the Sunday Style and Datebook sections, covering gala night openings and writing trend pieces. Her profiles of personalities have included fashion designer Diane von Furstenberg, Twitter co-founder Biz Stone and Emanuel Ungaro fashion house owner Asim Abdullah, to name a few. In a six-month project with The Chronicle’s investigative team, she recently revealed the misleading practices of a San Francisco fashion charity that took donations from wealthy philanthropists but donated little to the stated cause of helping the developmentally disabled. On the lifestyle front, her duties also including writing about cannabis culture for The Chronicle and its cannabis website, www.GreenState.com website.